1. Field of the Invention
This invention relates generally to door locks. In particular, this invention is concerned with a door latch release mechanism in which a pivotal striker or keeper is latched by a stop and releasable by rotation of the stop. In one embodiment, the invention includes an arrangement whereby the stop may be energised electrically to release the striker or energised electrically to lock the striker by use of a reversible armature or a similar arrangement.
2. Description of the Prior Art
Electrically operated door latch release mechanisms mounted on door frames and the like for locking or unlocking doors from remote locations--such as in security buildings--are known. There are many problems associated with known mechanisms. These include the failure of many prior art mechanisms to operate when a load is applied to the door. For instance, if a wind exerts force against the door or if a person leans against the door, the relationship between the striker and the latch may become distorted, so that deactivation of the latch does not free the striker.
Another problem arises from attempts at forced entry. In some prior art mechanisms, the striker is latched by a relatively small pin or the like and the exertion of force can cause this pin to bend or break, thus releasing the door in an unauthorised situation.
Many prior art mechanisms are difficult to clean or service because they lack ready access to working parts. Many are constructed with insufficient chassis strength. There is a need for a mechanism which can permit access to parts and which has a strong chassis.
In addition to the above, it is desirable to provide a door latch release mechanism which has a dual mode of operation, so that the mechanism can be converted from one which is latched when energised to one which is unlatched when energised. Dual mode operations have been disclosed in U.S. Pat. No. 4,211,44 and PCT Application No. PCT/SE84/00363, published under No. WO 86/02690, for example. However, there is a need for dual mode operations which are simple to convert and which minimise the risk of error on the part of the person effecting the conversion.